Theoretical Study of the Conformations and Strain Energies of [<i>n</i>,<i>n</i>]Metaparacyclophanes: Indication of Stable Edge-to-Face and Displaced Face-to-Face Conformers for <i>n</i> = 4

Abstract

We have studied [n,n]metaparacyclophanes-model compounds exhibiting edge-to-face and displaced stacked aromatic-aromatic interactions-using semiempirical calculations for n = 2-5 and ab initio calculations for n = 2-4. For n = 2 and 3, the strain energies govern the conformational preference, while for n = 4 and 5 the aromatic-aromatic and strain energies are equally important. The 3,12-dithio[4,4]metaparacyclophanes exhibit edge-to-face aromatic-aromatic intereactions, while the [4,4]metaparacyclophanes and 2,11-dithio[4,4]metaparacyclophanes exhibit displaced stacked aromatic-aromatic interactions.